Using portals ia a contradiction if they have never showcased/directly stated to use speed. They have always used on-screen hax such as portals.
Your MFTL+ vs IT example is a false equivalence as the MFTL+ feats do exist in this case. However the Immeasurable feats, not really, it was never said they do that through only speed, and characters who were powered from the DDB used portals, implying that the DDBs traveled in other timelines through portals as well.
Meh, would wait input from
@Ottavio_Merluzzo and
@Dominodalek about this.